The present invention relates generally to heart valve prostheses. More specifically, the present invention relates to heart valve prostheses which have a sewing cuff and which have a valve body that is rotatable relative to the sewing cuff.
Prosthetic valves are used to replace defective natural valves in human hearts. The prosthetic heart valves permit blood flow in one direction through the valve, and block blood flow in the other direction. In general, prosthetic heart valves include an orifice ring which forms the valve housing and which provides a central orifice or lumen for passage of blood. A valve mechanism, such as one or more occluders or leaflets, is mounted in the orifice and opens and closes to regulate the passage of blood. The housing and occluders collectively form the valve body. One such valve is disclosed in U.S. Pat. No. 4,276,658.
To attach the valve body to the tissue of the heart, typically a sewing cuff (also called a suture cuff) is provided. The sewing cuff for heart valve prostheses is generally a soft, flexible torus-like element through which sutures may pass to secure the sewing cuff, and consequently the heart valve, to the heart tissue.
One technique for attaching a sewing cuff to a valve body is illustrated in U.S. Pat. No. 4,276,658. In that embodiment, the valve body includes a groove that is used in coupling the sewing cuff to the valve body.
Another method of coupling the sewing cuff to the valve body is shown in U.S. Pat. No. 5,071,431 to Sauter et al. Sauter et al. discloses a heart valve where a sewing cuff is attached to a stiffening ring, with the stiffening ring being coupled to the valve body by a lock ring which rides in grooves in the outer periphery of the valve body and the inner periphery of the stiffening ring.
After a damaged or diseased natural valve structure is removed from the patient, the prosthesis is typically seated in the proper orientation and the sewing cuff is sewn to the peripheral heart tissue. Depending on the particular valve structure, care must be taken to ultimately orient the valve to ensure that the valving mechanism is in the most favorable anatomical position to provide proper blood flow and to ensure that the valve operates without interference from surrounding heart tissue. This must either be done before the sewing cuff of the valve is sutured into place, or if the sewing cuff is rotatable relative to the valve body (rotatable sewing cuff valve), this can be done after the sewing cuff is secured to the heart tissue. While this latter arrangement is convenient and can obviate the need to remove and resuture a valve to effect a rotation, a rotatable sewing cuff valve must meet several criteria.
For example, the torsional force required to rotate the valve body relative to the sutured cuff must be low enough so that the surgeon is able to rotationally position the valve with ease and without damage to the surrounding tissue. Once implanted, however, the valve body must maintain the desired position during the remainder of the surgery, and thereafter. Consequently, the torque required to initiate rotation must be great enough to prevent spontaneous rotation in vivo. Thus, the torsional force required to rotate the valve body within the sewing cuff should be predictable and fall within a narrow predetermined range such that the valve body may be easily rotated by the surgeon, yet is resistant to undesirable in vivo rotation once implanted.
The torsional force required to rotate the valve body relative to the sewing cuff will be determined by the manner in which the sewing cuff is retained on the valve body. Various methods have been proposed to rotatably secure the sewing cuffs of heart valve prostheses to the valve bodies. For example, U.S. Pat. No. 4,197,593 to Kaster et al. discloses a heart valve where a sewing cuff is sutured to a polymeric slip ring that slides along the surface of the valve body. U.S. Pat. No. 4,535,483 to Klawitter et al. discloses a heart valve where the sewing cuff is carried by deformable metal retainer rings that engage a stiffening ring disposed in and secured to a peripheral groove in the valve body. U.S. Pat. No. 5,104,406 to Curicio et al. discloses a heart valve where the fabric of the sewing cuff is stitched to a core, which directly abuts and rides the groove in the valve body. The core and the valve additionally sandwich the fabric along the annular space where the fabric is stitched to the core. U.S. Pat. No. 5,178,633 to Peters discloses a heart valve where the sewing cuff is coupled to the valve body by continuous fastener bands. The frictional engagement between the fabric tube and the valve body or xe2x80x9corifice ringxe2x80x9d is controlled by the internal diameter of the fastener bands, which may be manufactured with precision. U.S. Pat. No. 5,876,463 to Vanney et al. discloses a rotatable heart valve which employs a spring for actively and independently exerting a controlled force directed substantially radially inward onto the outer circumference of the heart valve prosthesis.
Although several rotatable sewing cuff valves are available, these prior art devices typically suffer from one or more shortcomings. These shortcomings may include but are not limited to complexity of manufacture, undesirable variation in torque needed for rotation, excessive bulk, or insufficient radiopacity. Therefore, a need exists for an improved rotatable heart valve prosthesis. Moreover, the desired torque characteristics should be repeatable from valve to valve without surgically significant variation. Limitations of space within the implant site require that the cuff retention mechanism preferably be compact. Preferably, the retention mechanism should provide enhanced radiopacity to the valve.
A prosthetic heart valve is provided that includes an orifice ring adapted to carry blood therethrough. An annular recess is formed in an outer surface of the orifice ring and has first and second axially spaced walls. A sewing cuff is adapted to be coupled to a native tissue annulus of a heart and includes an inner annular cuff portion adapted to conform to the first and second recess walls in the orifice ring. A cuff retaining ring extends around the inner annular fabric portion such that the inner annular cuff portion is positioned between the cuff retaining ring and the annular recess. The cuff retaining ring is further adapted to exert a substantially axially directed force directed against the annular cuff portion and first and second axially spaced walls of the annular recess whereby a controllable torque to rotate the cuff relative to the orifice ring is developed substantially due to friction between the first and second recess walls cuff portion and the annular recess.